I don’t get what you are saying. “Future malicious prosecution?” You mean like a defendant suing because he got prosecuted but found not guilty?????????? No such animal.
I can’t figure out what you are getting at.
Some future DA trying to make a name for himself might try to prosecute just because technically there is no statute of limitations for murder. The "no bill" gives quite a bit of protection against future prosecution of someone who kill in self-defense.